Born in Gisborne, New Zealand, Baynes most recently played for Union Olimpija of the Slovenian Basketball League in 2012-13. In 10 games he averaged 13.8 points and 9.8 rebounds in 26.2 minutes.

Baynes, 6-10/260, began his professional career in 2009-10 playing for Lietuvos Rytas of the Lithuanian Basketball League, a squad that went on to win the Lithuanian National Championship. In 2010-11 he played in Germany for EWE Baskets Oldenburg before joining Ikaros Kallitheas in Greece the following season.

In the summer of 2010 Baynes was named to the Australian senior national team and competed at the 2010 FIBA World Championship in Turkey. Baynes then represented Australia at the 2012 Olympic Games in London, where he averaged 7.5 points and 3.3 rebounds while shooting .656 (21-32) from the floor.

Baynes played collegiately at Washington State from 2005-09, where in 122 career games he averaged 8.7 points and 5.4 rebounds in 22.0 minutes.